1. Field of the Invention
This invention relates broadly to the field of electrically powered motors. More specifically, this invention relates to an improved electric motor and a method for winding an electric motor which is simpler and less expensive to perform than previously used methods, and which results in an electric motor winding which is more power efficient than windings heretofore known.
2. Description of the Prior Art
Alternating current (AC) and direct current (DC) brushless motors conventionally have an outer stator surrounding an inner rotor, the rotor being mounted to rotate within the stator.
In most electric motors, the stator includes a number of regularly spaced radially oriented teeth along its inner periphery, which define a corresponding number of slots. The teeth and slots extend along the entire axial length of the stator. Through various techniques which are well known to those skilled in the field, electrical windings are positioned in the slots between the teeth from one end of the stator to another, and around the teeth at the opposite ends of the stator. In this manner, the electrical windings are precisely oriented with respect to the rotor so that AC or switched DC voltage applied to the windings will induce a magnetic field which has a known, predetermined orientation. The electro-magnetic field is designed to react with permanent magnets or inductive windings on the rotor to turn the rotor in a desired direction.
It can be difficult and time consuming to install the electrical windings into a slotted stator, and a fair amount of complicated machinery has been developed over the years to do this. In addition to the manufacturing difficulties presented by the slotted stator configuration, the presence of the teeth which define the slots creates magnetic discontinuities, which can affect the efficiency of the motor. In addition, the presence of the teeth limit the number of windings which can be positioned in the critical area of the stator adjacent to the rotor. This, too, adversely affects the efficiency of the motor. If the entire area on the stator which is adjacent to the rotor could be filled with conductors, motor efficiency would increase, and losses due to factors such as hysteresis would be lessened.
Other forms of motor windings which eliminate stator teeth and slots are known, but most variously require specialized coil forms, specialized winding machines to provide coils of special geometry, or specialized support structures. Such structures are expensive and complicated to manufacture. As a result, despite their known disadvantages, most electrical motors are still being manufactured with the slotted stator configuration.
It is clear that there has existed a long and unfilled need in the prior art for a slotless winding for electrical motors which is inexpensive to manufacture, which is reliable, and which results in a higher winding density than was attainable by use of a slotted winding configuration.